The invention relates in general to sealant compositions applied to cured silica-containing materials, such as cement or concrete, to improve resistance to degradation caused by weather, chemicals and other corrosive elements. More particularly, the invention relates to sealants which penetrate to significant depth into the cured silica-containing material substrate and prevent alkali-silica reactivity within the substrate. Even more particularly, the invention relates to a sealant composition containing an alkali metal silicate and one or more surfactants.
Silica-containing materials such as cement or concrete are extremely common and are usually used in an environment exposed to corrosive, chemical, mechanical, thermal or atmospheric degrading elements. For example, rain water and road salt used to deice roads will penetrate the surface of the concrete and react with unreacted calcium compounds in the concrete to create a gel which expands and causes stresses and cracking,eventually degrading the concrete to the point where expensive repair or replacement is required. In most situations therefore it has been found beneficial to provide a protective coating or sealant to the surface of the silica-containing substrate to form a barrier layer to protect the substrate from the environmental hazards. Such coatings or sealants are preferably wear, chemical, water and ultraviolet light resistant, and must be of relatively low viscosity when applied to a cured substrate for optimal adhesion and penetration. Typical known coatings and sealants include components such as epoxies, polyurethanes, silicones, silicates, acrylics, vinyls, alkyds, or chlorinated rubbers. Many of the currently known sealants and coatings are hazardous to mix, have relatively high viscosities and are not highly effective for post-cure applications, mainly due to the inability of the sealant to penetrate to any significant depth below the surface of the cured and hardened silica-containing material.
It is an object of this invention to provide a sealant for post-cure application to silica-containing materials, such cement, concrete, stucco, masonry, plaster, limestone, etc., which increases the useful life of the material by protecting the substrate from environmental degradation caused by wear, chemicals, water, ultraviolet light, etc. It is a further object to provide such a sealant with greatly improved penetration properties relative to the currently known sealants. It is a still further object to provide such a sealant containing alkali metal silicates and a surfactant, whereby the surfactant maximizes penetration of the sealant into the substrate and the alkali metal silicates react with calcium compounds in the silica-containing material to form insoluble silicate structures to prevent environmental degradation over time from alkali-silicate reactions.